Re: [Matplotlib-users] psd

[David C. <dcd...@gm...>]

Hi, thanks for that. I've made the following changes:

NFFT = 100*60*10        # Linked to window size
Fs = stream[0].stats.sampling_rate
win = np.hanning(NFFT)
overlap = NFFT/2
power, freq = plt.psd(data, NFFT, Fs, win, overlap)

but it returns the following error:

Traceback (most recent call last):
  File "/home/davcra/Desktop/python_scripts/welchPSD.py", line 20, in
<module>
    power, freq = plt.psd(data, NFFT, Fs, win, overlap)
  File "/usr/lib/python2.7/site-packages/matplotlib/pyplot.py", line 2322,
in psd
    ret = ax.psd(x, NFFT, Fs, Fc, detrend, window, noverlap, pad_to, sides,
scale_by_freq, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/axes.py", line 7876, in
psd
    sides, scale_by_freq)
  File "/usr/lib/python2.7/site-packages/matplotlib/mlab.py", line 389, in
psd
    scale_by_freq)
  File "/usr/lib/python2.7/site-packages/matplotlib/mlab.py", line 419, in
csd
    noverlap, pad_to, sides, scale_by_freq)
  File "/usr/lib/python2.7/site-packages/matplotlib/mlab.py", line 268, in
_spectral_helper
    thisX = windowVals * detrend(thisX)
TypeError: 'int' object is not callable


On Mon, Jan 30, 2012 at 12:13 PM, Fabrice Silva <si...@lm...>wrote:

> Le lundi 30 janvier 2012 à 11:45 +0000, David Craig a écrit :
> > Hi I have some data for a 24hr period with a sample rate of 100
> > samples/second. I want to create a power spectrum using matplotlibs
> > function psd. I want it to have 10 minute windows with a 50% overlap,
> > but cant seem to get the syntax right. My code is as follows:
> >
> > NFFT = len(data)
> > Fs = 100
> > window=np.hanning(Fs*60*10)
> > noverlap = window*0.5
> > plt.psd(data, NFFT, Fs, window, noverlap )
> >
> > anyone kow how to do this properly???
>
> Be careful to use a suitable value for NFFT. It must be linked to your
> windows size, not the total data length, and you would rather use a
> power of 2 for efficience. Do not use it to increase the frequency
> resolution (use pad_to instead).
>
> Fs = 100
> NFFT = Fs*60*10
> Pxx, f = plt.psd(data, NFFT, Fs, window=np.hanning(NFFT), NFFT/2)
>
> --
> Fabrice Silva
>
>
>
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